Titanium-base alloys



Patented May 13, 1952 UNITED STATES PATENT OFFICE TITANIUM-BASE ALLOYSware No Drawing. Application March 2, 1951, Serial No. 213,690

Claims. (Cl. 75-134) 1 This invention relates to titanium-base alloys,and particularly to ternary alloys of titanium and aluminum with boron.

The use of titanium as a structural material is at a given strengthlevel, the quantity of each which can be tolerated depends to aconsiderable extent upon the quantity of the others. The limiting factoris usually ductility, and the relimited by its relatively low strengthand high 5 quirement as to ductility varies with the intended cost, andit becomes desirable to alloy titanium use of the alloy. Further,increasing the with such other metals as will increase the amounts ofthe substitutional metallic alloying strength to acceptable levels andpreferably at ingredients tends to decrease the tolerance for the thesame time effect some reduction in the total interstitital components,particularly embrittling material cost. Aluminum is a metal well suitednitrogen. An alloy of high purity titanium with to the attainment ofthese objectives, being low in 5% aluminum will tolerate as much as 0.25weight, relatively low cost, and having amaterial nitrogen, but theaddition of one or two percent strengthening effect on titanium.However, the of another metal materially reduces nitrogen amount ofaluminum alone that can be added to tolerance. titanium is limited byits adverse effect on duc- The alloys of this invention may be preparedtility. Binary alloys of titanium with more than by melt-casting i anatmosphere of argon, 1 about 5% 0f aluminum are tOO brittle for most ingat a, uitable temperature, say 980 (1., and stru tu al us s; a d suc a yalloys a annealing under conditions which will effect res less n b ualuminum do not crystallization, but not substantial grain growthpossess sufficient strength to be of general utility. or re solution ofcarbides A typical but by no A further strenethemng 1S hlgmy meansuniversal annealing treatment comprises The present invention comprisesthe discovery Soaking at a temperature f about 0 f r that the additionto titanium-aluminum alloys of about 1 hours The rate f cooling ft 9 toabout; 05% of borcfn effecls marked nealing is not material, since inthese alloys the improvement in the properties of t1tan1um-alutitaniumis an in the alpha phase except for minum alloys of a given aluminumcontentzsay minor amounts which may be combined as titato alloys Show ai combma' nium carbide. The properties of selected alloys tion, 9extraordmary Strength Wlth adequate of titanium of requisite purity withaluminum ductlhty and tin, as annealed for 3%.; hours at 850 0., un-

The metal used as a base for the alloys of the less otherwise noted areas follows.

present invention may contain the interstitial The properties of g alloyof subsantiauy pure contaminants carbon" oxygen. and/Or titanium with 5%aluminum, as annealed for 3 up to at least the total quantity to befound in hours at are as follows. good quality commercial titanium.Carbon, for example, has been found to be beneficial when ProportionalLimit, 1 43,000 present in amounts between 0.02% and 0.3%, the 0 ofi etyield Strength i 51000 latter being about the maximum amount which is 0Ofiset Yield strength i 09 soluble in alpha titanium. An excess ofcarbon t t Strength 79 00 tends to form embrittling carbides. For atypip t Ehmgation, in 1 inch 13 cal alloy, a carbon content of 0.1% to0.2% is Minimum Bend Radius desirable, but the optimum amount varieswith other factors. Nitrogen is a potent hardener of The properties ofselected alloys embodying the titaniumbut tends to cause embrittlement.The present invention, as annealed for 3 hours at effect of the threecontaminants being additive 850 C., are as follows:

Composition Tensile Properties-p. s. 1.

(Balance Titanium) Propor- 0 2% Elongn B $35??? n 5 1.0 378 117,000 124.000 135, 000 7 Brittle thickness, to which the specimen can be bent toan angle of 75 without fracture.

It will be seen that the addition of as little as 0.1% of boron effectsa substantial increase in strength as compared with the strength of anotherwise identical alloy without boron, and that ductility is actuallyslightly increased rather than diminished. Increasing the boron contentto 0.5% produces a further increase in strength with an almostnegligible efiect on ductility. At a boron content of 1 the strengthlevel is about double that of the titanium-5% aluminum base, and enoughductility remains for a wide variety of uses, about the only useexcluded being sheet and other forms which are stretched in fabrication.

'The alloys are characterized by a fine grain structure, average grainsize being from 0.017

mm. to 0.022 mm., and by the presence in a matrix of alpha titanium ofdispersed particles of a second phase, believed to be titanium boride.The solubility of boron in the titanium-5 aluminum base is thus lessthan 0.1 and there is experimental evidence that its solubility in betatitanium is not materially different. The presence of the insolublesecond phase particles is, as in other related alloys, associated withfine grain structure and a spread of several thousand p. s. i. betweenyield strength and ultimate strength, with the enhanced utilityresulting therefrom.

The alloys having the properties tabulated above were made by the use ofamorphous boron. While crystalline boron may be used, it appears to bemore difilcult to melt, and incomplete melting may yield inconsistentresults.

What is claimed is:

1. An alloy consisting essentially of from 3.5% to 5% aluminum, from0.1% to 1% boron, balance titanium. I 2. An alloy consisting essentiallyof from 3.5% to 5% aluminum, from 0.1% to 1% boron, from 0.02% to 0.3%carbon, balance titanium,

3. An alloy consisting essentially of from 3.5% to 5% aluminum, from0.1% to 0.5% boron, balance titanium.

4. An alloy consisting essentially of about 5% aluminum, from 0.1% to 1%boron, balance titanium. t Y

5. An alloy consisting essentially of about 5% aluminum, from 0.1% to0.5% boron, balance titanium.

ROBERT I. J AFFEE. HORACE R. OGDEN. DANIEL J. MAYKUTI-I.

No references cited.

1. AN ALLOY CONSISTING ESSENTIALLY OF FROM 3.5% TO 5% ALUMINUM, FROM0.1% TO 1% BORON, BALANCE TITANIUM.